Doubles w/Stage on a 30# wing

[Halthron]

That's what I was missing, having the wing stuck between the tank & the plate. Definately something to verify both on land and in the shallows before actually following through with this guy's comments. Thanks!

 

[Halthron]

I'll also second the concern that you are on the edge already with tanks, bands, regulators and stage bottle and have little if any margin to compensate for wetsuit compression at depth.

The words "doubles", "stage bottle", and "ditching lead" used in the same paragraph also make me extremely nervous. Ditching lead should always be a last resort as it will in most circumstances result in an ascent all the way to the surface - something that is just not an option on a deco dive. This would certainly be the case if you dropped lead on the bottom to offset wetsuit compression.

Wetsuits used here tend to be of the rashguard variety, thin shorties or the thinnest fullsuit the person owns, something I had already taken into account. I used "ditching weight" more as a compensation for the wing if it were underspec'd and if the tanks were overspec'd. Of course, if deco had been aquired, the tanks themselves would be more bouyant as well. "Ditching" would only need to be done at the beginning in the event something happened.

Of course, the possibility of the wing being stuck and not being able to inflate fully is what I missed, which is why I'm glad I don't just listen to someone with more experience than I but come here for aditional confirmation. Thanks for that info.

 

[cyklon_300]

double AL80s, AL40 deco bottle, 3-mm two-piece wetsuit, 7-lbs wt, and 30-lb Oxy singles wing.

The wing, when fully inflated, was only marginally restricted and provided ample flotation at the surface. No problems diving to 135'.

 

[ianr33]

And then there are always those other factors like:

Extra weight of.....


e) redundant air source (spare air?)


This all might sound really obvious but it all adds up to negative weight. It all adds up quick.

I agree...dumping weight should not be the option to make the system work

Haven't seen too many people diving with doubles,stage and a Spare Air

 

[roakey]

I was talking with a technical instructor for ANDI/TDI earlier today and he mentioned having used doubles (AL 80s) with an Al 80 stage bottle on a 35 lb wing. The more I thought about it, I thought, why not? A full Al 80 is negative by what, about 2 lbs? Three of them is 6 and if you're using a SS plate, that's another 5-6 lbs. Then 14 lbs of lead to offset the bouyancy those three tanks would have when empty and you're at 26 lbs.

Am I missing something here? Sure, not every 30 lb wing is really 30 lbs you need to expect +/- 1-2 lbs. but the total is still under the fudge value. Is there some reason I'm missing why this wouldn't work, especially if some of that lead was ditchable?

The absolute negative buoyancy of the cylinders isn't the important thing here, it's the swing of the cylinders and (I'll assume) wetsuit. Those are the only variable buoyancy items in your kit (ignoring your lungs).

So, assume that you select your gear such that you're perfectly neutral at the surface with an empty wing and zero PSI in all three AL80s. Now, fill the AL80s; they swing about 6 pounds each = -18 pounds. You've got 12 pounds of lift to spare now. How much lift do you lose with wet suit compression? A double layer 7mm will probably lose more than 12 pounds at depth, and you'd be in a world of hurt. If the water's warm enough that you don't need a wetsuit (to look at the other extreme) and there's no compression (no suit!) so you have that full 12 pounds to play with. Maybe that's enough, maybe it isn't if the water's rough and you want to get you head a bit higher out of the water -- your call.

Roak

 

[jagfish]

Haven't seen too many people diving with doubles,stage and a Spare Air

:05:

 

[paolov]

them tanks won't go empty as the rule of thirds prevail. at depth if anyone of the group reaches that limit the group all follows the most conservative .

And as far as the wing getting stuck on the doubles... never happened. the preparation makes the dive fail safe.

also the weight used by the diver/s is around 2 to 6 lbs only assuming these are done in warm water area.. and calm seas

from our experiences here.

I was talking with a technical instructor for ANDI/TDI earlier today and he mentioned having used doubles (AL 80s) with an Al 80 stage bottle on a 35 lb wing. The more I thought about it, I thought, why not? A full Al 80 is negative by what, about 2 lbs? Three of them is 6 and if you're using a SS plate, that's another 5-6 lbs. Then 14 lbs of lead to offset the bouyancy those three tanks would have when empty and you're at 26 lbs.

Am I missing something here? Sure, not every 30 lb wing is really 30 lbs you need to expect +/- 1-2 lbs. but the total is still under the fudge value. Is there some reason I'm missing why this wouldn't work, especially if some of that lead was ditchable?

 

[ianr33]

them tanks won't go empty as the rule of thirds prevail. at depth if anyone of the group reaches that limit the group all follows the most conservative .

And as far as the wing getting stuck on the doubles... never happened. the preparation makes the dive fail safe.

also the weight used by the diver/s is around 2 to 6 lbs only assuming these are done in warm water area.. and calm seas

from our experiences here.

Yeah but what happens when one diver has a freeflow or other failure and you end up sharing air with one divers tank empty and the other at 500 pounds?

You can not assume you will absolutely have gas left at the end of the dive,otherwise why bother taking it??

 

[paolov]

so far never happened. in the event, we have a standby tank at 20ft hovering us. now this is part of the dive plan we do. we don't do this on overhangs.

Yeah but what happens when one diver has a freeflow or other failure and you end up sharing air with one divers tank empty and the other at 500 pounds?

You can not assume you will absolutely have gas left at the end of the dive,otherwise why bother taking it??

 

[Ron Brandt]

The wing needs to be able to float the rig,without you in it.
Ron